This invention applies to the field of hydrodynamics, and relates to the use of gas cavities to reduce the frictional drag of ship hulls.
The reduction of frictional drag provides basic benefits: power is reduced, and fuel consumption is reduced. These benefits reduce the weight of a vessel, which further reduces power and fuel consumption compared with a fully wetted vessel designed for a given payload and range. Alternatively, vessel speed can be significantly increased with the same displacement, power, payload and range. Cost and time for payload delivery are greatly reduced by reducing drag.
Past work on the use air cavities to reduce hull drag includes different kinds of surface effect ships (SES). These vessels use a pocket of compressed air on the underside of a vessel to support the weight of the vessel and reduce frictional drag. SES design speeds range from low to very high. Some SES vessels resemble conventional ships with the addition of bottom side fences and bottom forward and aft barriers to contain a pocket of pressurized air. Other SES vessels have catamaran hulls with cavities under the hulls to contain pockets of pressurized air.
Although drag is significantly reduced by SES craft, considerable wetted surface area remains, together with significant wavemaking drag and other sources of drag including the drag of side fences.
The problem is how to design underwater surfaces to make full use of air cavities to minimize wetted surface area and maximize drag reduction. The need clearly exists for improved low drag ship hulls.